Which camera lens should I film with?

KFTV makes sense of the vast camera lenses market and looks at the models that could have the biggest impact in the coming years.

There seems to be almost no end to the lens market, especially for the big, expensive models that would usually be used on a feature film or single-camera drama.

The recent International Broadcasting Convention (IBC) offered new arrivals. Sigma, who had previously only made lenses for still photography, announced a comprehensive new range, and Zeiss showed a new lightweight zoom which seems very much intended for documentary and handheld camerawork.

There are so many new options on the market that it's clear something new has happened in recent years – a wholesale change in how cameras and lenses work together, and the sort of productions which use them.

The driving force behind this is the growth in what a camera specialist might call ‘big-chip’ cameras. Since the 1970s at least, imaging sensors in the sort of video cameras used for news and current affairs have been about eight by six millimetres. That's small compared to the size of a 35mm film frame, at anything up to 24mm by 19mm.

Big sensor sizes

The bigger sensor size can afford productions a quality that's rather vaguely described as ‘cinematic’, which tends to mean that objects other than the intended subject tend to fall into out-of-focus softness more quickly. Bigger sensors can also be less prone to noise and graininess, more sensitive in low light and less likely to produce ugly white glare when shooting bright subjects.

So, the drive for digital cameras with large sensors was significant through the 2000s, and crews often prefer them. On one hand, this is great. Big-sensor cameras, such as Sony's F series (pictured left), have become affordable to productions which would traditionally have used smaller sensors.

A central problem, however, is that the sort of lenses that are designed for documentary and news work just don't project an image big enough to satisfy big-sensor cameras. They could be mounted, physically, using an adaptor, but without corrective optical parts the picture would look like a black screen with a circle of image in the middle.

It's easy to overlook what a big deal this can be to camera operators. People with decades of experience shooting news are very much habituated to the way that a video zoom lens works, with all of the controls easily laid out and a grip on the right hand side. The lens of a news camera forms a huge part of the way the camera is held and used.

Compare the lenses used for single-camera work on drama and features. They're generally ‘prime lenses’, meaning that if we want to zoom in, you have to change lenses. There is no handgrip and even things like the focus action are inconvenient for handheld work, requiring the focus ring to be rotated through almost a full turn to get from one end to the other.

When there's a focus puller on hand, this makes for precision, but working solo it's difficult. Traditional video zooms tend to require half a turn or less, which can be done by hand without letting go.

These issues mean missed focus, missed shots and ultimately compromises to the production. The solution is a lens for large-sensor cameras that operates like the traditional video zoom.

The Fujinon ZK4.7x19 (pictured right) was the first and possibly best-known of these, although Canon's competing CN7x17 is possibly even more like a newsgathering lens, with the shorter focus rotation. From an engineering perspective, this is a difficult project: to create a larger image – all other things being equal the lens must be larger.

Almost simultaneously with the rush to large-sensor cameras, we've also encountered HD and then 4K, which demand more optical precision.

Technical choices

Being both bigger and more precise, it's no surprise that the Fujinon and Canon lenses are expensive. A freelancer might be able to pick up a reasonable used video zoom lens for a few thousand pounds – certainly less than ten. The Fujinon, however, costs over £21,000, and the Canon nearly £20,000, putting it well into the frowning-producer zone in terms of a per-day rental. They're fantastic lenses, but they're also heavy enough to be inconvenient on many cameras.

Because of all this, other solutions have emerged. MTF Services manufacture an adaptor that will expand the image of a traditional video zoom to cover a large sensor, and Sony make a custom device, the LA-FZB1, which does more or less the same thing for their F5 and F55 cameras.

There are caveats. The optical quality, while reasonable, is not on a par with the Canon and Fujinon lenses, and the expansion of the image means that more light is required for correct exposure. It's less likely that anyone would buy a traditional video zoom with the intention of mounting it on one of these adaptors, although they make a lot of sense as a rental or for people who may already own the requisite lens.

So, until 2016, the choices were stark. Camera operators using large-sensor cameras for traditionally small-sensor work had excellent but heavy and expensive options from Canon and Funinon, or adaptors with their old video zooms, or even the purgatory of lenses designed for still photography which often don't have proper focus controls at all.

This problem was recognised as an opportunity by Canon, who introduced their CN-E 18-80mm zoom lens at the National Association of Broadcasters 2016 and announced a price of around £4,500. It's built more like a modified stills lens than a video lens, it will require extra light compared to more expensive options and it doesn't have a huge zoom range. Still, it's well-priced and the company can expect to sell thousands of them.

For those interested in something closer to a video zoom, the surprise at IBC was Zeiss's LWZ.3 (pictured above), a 21-100mm lens of rather greater capability which will sell for around £8,500. It lacks a handgrip and the focus rotation is a little too long, but it's financially practical for self-employed camera people.

The situation is improving. There's still a question mark over whether large-sensor cameras are really appropriate for all the productions they're used on; smaller-sensor devices have improved as well, and we can achieve results satisfying many definitions of the word ‘cinematic’. At the very least, we can now make these decisions in full knowledge of the knowledge of the compromises that are necessary, and the sort of equipment that's required to give the camera operator the best tools for the job, and when Zeiss's zoom comes out there'll be a powerful new option available.